This invention relates in general to imaging systems, and, more specifically, concerns an improved migration imaging system.
There has been recently developed a migration imaging system capable of producing images of high quality and excellent resolution. This system is described in detail and claimed in application Ser. No. 403,002, filed Oct. 12, 1964, now abandoned. In a typical embodiment of this imaging system, a layer of a softenable material is coated onto a substrate and a fracturable photoconductive layer is formed contiguous to the surface of the softenable layer, thereby forming an imaging member. The fracturable marking material may also be particulate and the softenable layer which may be soluble in a solvent which does not attack the fracturable layer. An electrostatic latent image is formed on the surface of the fracturable layer, or the member is uniformly electrostatically charged and exposed to a pattern of activating electromagnetic radiation, and then the softenable layer is softened, for example by dipping the plate in a solvent. Portions of the fracturable layer migrate in imagewise configuration through the softenable layer as it is softened or dissolved, leaving an image on the substrate conforming to a negative or positive of the original (depending upon the imaging materials and processing variations used). Those portions of the fracturable layer which do not migrate to the substrate, and the softenable layer may be washed away with a solvent for the softenable layer. The image resulting is of high quality and of especially high resolution. Alternative embodiments are further described in the above cited copending applications.
Another variation of migration imaging for example as described in copending application Ser. No. 483,675, filed Aug. 30, 1965, now U.S. Pat. No. 3,656,990, may use non-photoconductive particles coated over a non-photoconductive soluble layer on a substrate. Here, an electrostatic latent image is formed as by corona charging through a stencil. When the imaging member is exposed to a solvent for the softenable layer, particles migrate to the substrate in imagewise configuration. Undesirable particles are washed away with the soluble layer. While this imaging process does not require but may use photoconductive materials, the charge pattern is typically applied in imagewise configuration, e.g., by corona charging through a stencil.
Each of these imaging systems is capable of producing excellent images. However, each system has its own inherent advantages. The first system described above requires that the fracturable layer comprise an electrically photosensitive and typically a photoconductive material. Ordinarily this layer is in the form of particles. Some of the photoconductors produce more desirable images than others. Often, the color of the photo-conductive particles is other than black so that the final image produced is other than black-on-white. Typical useful photoconductors in this system include dark red selenium, and blue-green phthalocyanine.
In the second system described above the electrostatic latent image typically must be originally formed in imagewise configuration. Such images are typically produced from a stencil or similar means.
In new and growing areas of technology such as migration imaging systems, new methods, apparatus, compositions and articles of manufacture are often discovered for the application of the new technology in a new mode. The present invention relates to a new and advantageous migration imaging system using photoconductive softenable materials.